Update button in EditForm

[Iris]

I have an Update button in template editForm. My problem is that I cannot implement the button. I have seen this demo (http://demos.telerik.com/aspnet-ajax/grid/examples/dataediting/usercontroleditform/defaultcs.aspx) and tried to implement the RadGrid1_UpdateCommand event handler, but I got compilation errors for this line:

DataRow[] changedRows = this.UserDataSource.Select("user_id = " + editedItem.OwnerTableView.DataKeyValues[editedItem.ItemIndex]["Users"]);

The errors are:
1. "The best overloaded method match for 'System.Web.UI.WebControls.SqlDataSource.Select(System.Web.UI.DataSourceSelectArguments)' has some invalid arguments"
2. "Argument 1: cannot convert from 'string' to 'System.Web.UI.DataSourceSelectArguments'"

Can anyone help me on this?

Here's the code for the UpdateCommand event handler:

protected void RadGrid1_UpdateCommand(object sender, GridCommandEventArgs e)
{
   GridEditableItem editedItem = e.Item as GridEditableItem;
   UserControl userControl = (UserControl)e.Item.FindControl(GridEditFormItem.EditFormUserControlID);

   //Prepare new row to add it in the DataSource
   DataRow[] changedRows = this.UserDataSource.Select("user_id = " +
        editedItem.OwnerTableView.DataKeyValues[editedItem.ItemIndex]["Users"]);

// in progress. to be implemented here
}